Five things you might not know about leap years

Leap-year babies, also referred to as ‘leaplings’ or ‘leapers’ are those who are born on that extra day during a leap year, which happens, roughly - but not exactly every four years.

February 29 is a rare occasion to experience but plays a significant role in keeping our annual calendar and the passing of the seasons aligned over very long timescales. 

Despite a bizarre historical origin and a series of urban legends surrounding it, Leap Day exists for scientific, not superstitious, reasons.

While the modern Gregorian calendar states there are 365 days in a year, scientifically speaking there are actually 365.2422 days. That's almost exactly the amount of time it takes the Earth to go around the Sun, and technically how many days are in a year. 

The difference of five hours, 48 minutes and 46 seconds might seem negligible, but over decades and centuries that missing quarter of a day per year can add up. 

Without a Leap Day, the physics of planet Earth would quickly cause the seasons to move out-of-phase with our annual calendar, and the equinoxes and solstices would drift around the days, months and seasons.

To celebrate the 2020 Leap Year, we want to share five somewhat lesser-known facts about these rare occasions.

Why February?

The reason Leap Day is in February is primarily down to history. Back in the 8th century BC, years were only ten months long. Then Romans came along and added January on to the end of the year. February - the final month in this calendar got fewer days. 

Julius Caesar then tweaked the calendar to line it up with the sun. In a decree, he added a Leap Day. The Leap Day still didn’t fully account for the differences, so in 1582, Pope Gregory XIII created the Gregorian calendar and established February 29 as the official date.

Not quite every four years

Technically speaking leap years are not exactly every four years. Since the 16th Century, leap years have been calculated by whether the year is divisible by 100. Years that are divisible by 100, like 1900, are skipped, unless they're also divisible by 400, like the year 2000 - in which case they're observed. Nobody alive remembers the last ‘lost’ leap day, but dropping those three leap days every 400 years keeps the calendar aligned.

Unlucky for some?

Some people in Scotland say that being born on Leap Day is bad luck - comparable to the unlucky Friday the 13th, also thought to carry misfortune. 

For Scottish farmers, many worry for their livestock during leap years, with an old saying of: “Leap year was never a good sheep year”.

In Greece it’s considered unlucky to get married during a leap year, but especially on Leap Day. According to the Greeks, leap year marriages will almost certainly end in divorce. 

Annual salaries

If you’re paid a fixed annual salary, it’s highly likely you won’t get paid more because it’s a leap year. This means technically speaking, anyone working on Leap Day is actually working for free!

Leap-less calendars

Even today, some calendars discount the leap year designed to keep us in time with our orbit, while others ignore the sun altogether.

The Islamic calendar is a lunar system that adds up to only 354 days and alters a whole 11 days from the Gregorian calendar each year - though a single leap day is sometimes added.

China uses the Gregorian calendar for official purposes, but a traditional lunisolar calendar is still popular in everyday life. It follows the phases of the moon and implements an entire leap month, around once every three years.